Boat tower



FIG. 1 is a front perspective view of a boat tower showing my new design, the broken lines are for illustrative purposes only and form no part of the claimed design;

FIG. 2 is a side elevational view thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a top plan view thereof; and,

FIG. 5 is a rear view thereof. 

The ornamental design for “boat tower”, as shown and described. 